Gunmen attacked a church in volatile northern Nigeria during a Christmas Eve service, killing six people including the pastor, before setting the building ablaze, residents and police said Tuesday, as the pope deplored "savage acts of terrorism" against Christians in Africa's most populous nation.

The raid in Yobe state is the latest violence likely to be blamed on radical Islamist sect Boko Haram, which has repeatedly targeted churches during times of worship, including multiple attacks last year on Christmas Day, during its deadly insurgency.

In his traditional Christmas message from the Vatican, Pope Benedict XVI prayed for "concord in Nigeria, where savage acts of terrorism continue to reap victims, particularly among Christians".

"A group of gunmen came into the village at midnight and went straight to the church," said Usman Mansir, a resident of Peri village near Potiskum, the economic capital of Yobe. "They opened fire on them, killing the pastor and five worshippers. They then set fire to the church," he added, specifying that a branch of the Evangelical Church of West Africa (ECWA) was targeted.

A senior police official in Yobe confirmed the details of the attack to AFP, but declined to be named, while Yobe's police chief Sanusi Rufa'i said "this is a security issue" and refused to comment further.

The head of the Christian Association of Nigeria in Yobe, Idi Garba, told AFP that many worshippers at ECWA "are still missing." "I have been informed that six bodies have been recovered," Garba said, adding that some who lived near the church "fled their homes during the attack and it is assumed that they are still hiding in the bush."

Residents reported that the gunmen also set fire to several of the homes surrounding the church.